What type of vaccine is Gardasil-9 (human papillomavirus vaccine)?

Type of Vaccine for Gardasil-9

Gardasil-9 is a non-infectious, virus-like particle (VLP) recombinant vaccine that contains 9 HPV types (6,11,16,18,31,33,45,52, and 58) adsorbed on amorphous aluminum hydroxyphosphate sulfate adjuvant. 1, 2

Composition and Manufacturing

• Gardasil-9 is prepared from fermentation cultures of a recombinant strain of yeast (Saccharomyces cerevisiae) containing the genes for the human papillomavirus L1 protein of each of the nine included HPV types 1
• The vaccine contains no preservatives or antibiotics 1
• Each 0.5-mL dose contains specific amounts of HPV L1 protein: Type 6 (30 mcg), Type 11 (40 mcg), Type 16 (60 mcg), Type 18 (40 mcg), Type 31 (20 mcg), Type 33 (20 mcg), Type 45 (20 mcg), Type 52 (20 mcg), and Type 58 (20 mcg) 1

Mechanism of Action

• The vaccine works by inducing type-specific and neutralizing antibodies that prevent HPV infection 3
• The L1 proteins self-assemble into virus-like particles that are identical to the complete virion but contain no viral DNA, making them non-infectious 4
• This structure triggers an antibody-mediated immune response before the body encounters the actual virus 4

Evolution from Previous HPV Vaccines

• Gardasil-9 is an evolution from the quadrivalent HPV vaccine (4vHPV, original Gardasil) which contained only HPV types 6,11,16, and 18 2, 5
• As of January 2017, Gardasil-9 became the only available HPV vaccine in the United States, replacing both the quadrivalent Gardasil and the bivalent Cervarix 2
• The addition of five more oncogenic HPV types (31,33,45,52, and 58) increased potential protection against cervical cancer from approximately 70% to approximately 90% 3, 2

Clinical Significance

• The 9vHPV vaccine has demonstrated 97% effectiveness in protecting against cervical, vulvar, and vaginal cancer precursor lesions related to the 5 additional types included beyond the original quadrivalent vaccine 2
• HPV types 16 and 18 (included in all HPV vaccines) are responsible for approximately 70% of HPV-related cancers 2
• The additional five HPV types in Gardasil-9 are responsible for an additional 14% of HPV-related cancers in women and 4% of HPV-related cancers in males 2
• HPV types 6 and 11 (included in both 4vHPV and 9vHPV) are responsible for 90% of genital warts 2

Administration and Recommendations

• Gardasil-9 is administered intramuscularly in the deltoid muscle of the arm or the anteriolateral area of the thigh 4
• Currently recommended as a 2-dose series for persons initiating the vaccine series from 9 through 14 years of age, with doses separated by 6-12 months 2
• A 3-dose series is recommended for persons initiating vaccination at ages 15 through 26 years 2
• In 2019, the ACIP expanded recommendations to include shared clinical decision-making regarding potential HPV vaccination for adults aged 27 through 45 years 2

Safety Profile

• Clinical trials have demonstrated a safety profile comparable to the original quadrivalent HPV vaccine 3
• The most common adverse reactions are injection site reactions, which may be more common with Gardasil-9 than with the original quadrivalent vaccine 6
• No serious safety concerns have been identified in clinical trials 6

Gardasil-9 represents a significant advancement in HPV vaccination technology, offering broader protection against HPV-related diseases while maintaining the safety profile of earlier vaccines.